Ground cover for containment barriers

ABSTRACT

A ground cover for use as a containment barrier including a geomembrane sheet and a geotextile sheet bonded together by an adhesive layer positioned therebetween. The adhesive layer does not fully cure, remains tacky and has an adhesive strength sufficient to maintain a bond between the geomembrane sheet and the geotextile sheet under normal foot traffic and a release point allowing separation of the geomembrane sheet and the geotextile sheet under shear forces generated by heavier traffic.

FIELD OF THE INVENTION

This invention relates to containment barriers.

More particularly, the present invention relates to sheet materialscovering the ground for use as containment barriers.

BACKGROUND OF THE INVENTION

In industries that have the potential to contaminate the environment,such as oil wells, gas wells, induced hydraulic fracturing sites,storage sites, mining operations, and the like, it is often desirous toprovide a means to protect the environment from contamination, andreduce the cost and complexity of spill cleanup. At drilling sites, manypotential contaminating fluids are used. Depending on the type ofdrilling being performed, various fluids can include drilling mud,fuels, fracturing chemicals, corrosives and flowback water. Spills ofany of these liquids must be cleaned from the environment. If the soilat the drill site is contaminated, the contaminated soil must beremediated. To reduce the amount of contaminated soil and water and toeliminate regulatory fines, many operating companies excavate the site,cover it with stone or crushed rock, place a geotextile over the crushedrock, and then loosely place a geomembrane over the surface. Ageotextile is typically a strong synthetic fabric used in civilengineering that stabilizes loose soil. Geotextiles are permeablefabrics which generally come in three basic forms: woven, needlepunched, or heat bonded. The geotextile protects the geomembrane fromsharp edges in the stone or crushed rock base. The geomembrane isnon-permeable and contains the leaks and spills for subsequent removal,e.g., until an on-site vacuum truck can remove them without impact tothe environment.

There are issues with this type of containment barrier. Traditional HDPEgeomembranes for ponds and pits were not designed for foot and vehicletraffic. HPDE geomembranes are prone to punctures, e.g., from droppedhoses, vehicles and equipment movement. The geomembranes are alsoextremely slippery to work on, even with a textured surface. Frictiontreatment of geomembrane or geotextile surfaces to prevent slippage isdisclosed in U.S. Pat. Nos. 5,056,960 and 5,137,393, respectively. Toincrease traction in standing water, snow and ice, some operatingcompanies place, but do not bond, an additional layer of a geotextileover the HDPE geomembrane to reduce slip hazards. However, in thisapplication, the geotextile slides on the geomembrane, producing a sliphazard and additionally, the geotextile is subject to wrinkling,bunching up or folding to produce trip hazards. The loose material canalso be pulled into vacuum hoses while removing liquids from thesurface. The loose geotextile can mask punctures in the geomembranebeneath it, which may only be discovered after a spill or leak.

A polymer sheet that has geotextiles affixed by mechanical engagement onboth sides is disclosed in U.S. Pat. Pub. 2012/0219746. This structureaffixes the layers by embedding a portion of the geomembrane into thegeotextile to prevent separation. While this prevents movement betweenthe layers, repairing damage in the containment liner can be difficultsince the layers cannot be separated. The entire damaged portion must bereplaced. Additionally, while the top layer of geotextile will protectthe geomembrane from punctures and the like, the flexibility of thegeotextile is greater than the geomembrane. Thus, when heavy vehicles orobjects are moved across the surface and have a change in direction,shear forces on the liner can cause a tear in the geomembrane or cancause a tear in the geomembrane and the geotextile. This tear willprevent proper containment, is difficult to repair and may go unnoticedif the geotextile is not damaged.

It would be highly advantageous, therefore, to remedy the foregoing andother deficiencies inherent in the prior art.

An object of the present invention is to provide a ground cover for useas a containment barrier that will allow both foot and vehicle traffic.

SUMMARY OF THE INVENTION

Briefly, to achieve the desired objects and advantages of the instantinvention provided is a ground cover for use as a containment barrier.The ground cloth includes a geomembrane sheet having a first surface anda second surface, a geotextile sheet having a surface overlying thefirst surface of the geomembrane sheet, and an adhesive layer positionedbetween the first surface of the geomembrane sheet and the surface ofthe geotextile sheet. The adhesive layer does not fully cure and remainstacky, the adhesive layer having an adhesive strength sufficient tomaintain a bond between the geomembrane sheet and the geotextile sheetunder normal foot traffic and a release point allowing separation of thegeomembrane sheet and the geotextile sheet under shear forces generatedby heavier traffic. The adhesive layer is present in an amount of 0.01to 0.1 ounce per square foot of surface and is a pressure sensitiveadhesive.

In a further aspect of the invention, the ground cover includes a secondgeotextile sheet having a surface overlying the second surface of thegeomembrane sheet. A second adhesive layer is positioned between thesecond surface of the geomembrane sheet and the surface of the secondgeotextile sheet. This second adhesive layer may include an adhesivethat does not fully cure and remains tacky. The second adhesive layermay have an adhesive strength sufficient to maintain a bond between thegeomembrane sheet and the geotextile sheet under normal foot traffic anda release point allowing separation of the geomembrane sheet and thegeotextile sheet under shear forces generated by heavier traffic.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further and more specific objects and advantages ofthe instant invention will become readily apparent to those skilled inthe art from the following detailed description of a preferredembodiment thereof taken in conjunction with the drawings, in which:

FIG. 1 is a sectional perspective view of a ground cover according tothe present invention;

FIG. 2 is a sectional perspective view of the ground cover of FIG. 1showing a separation;

FIG. 3 is a sectional perspective view illustrating an adhesive repairlayer; and

FIG. 4 is a sectional perspective view of another ground cover accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings in which like reference characters indicatecorresponding elements throughout the several views, attention is firstdirected to FIG. 1 which illustrate a ground cover 10 according to thepresent invention. Ground cover 10 is intended to be employed as acontainment barrier to prevent contaminants from reaching the soil.Ground cover 10 covers an area to be protected, and contains any spillsoccurring in the area until they can be cleaned, collected and removed.Ground cover 10 includes a geomembrane sheet 12 having a surface 14, ageotextile sheet 15 having a surface 16 overlying surface 14, and anadhesive layer 18 carried between surface 14 and surface 16. As will bedescribed presently, the adhesion strength between geomembrane sheet 12and geotextile sheet 15 is essential to the invention. Geomembrane sheet12 is substantially any impermeable membrane (usually made of syntheticpolymers in sheets) used with soils, rock, earth, or other geotechnicalmaterial in order to block the migration of fluids. In the presentembodiment, geomembrane sheet 12 is a 24 mil or 30 mil woven coatedpolyethylene. Woven coated polyethylene products are high densitypolyethylene threads woven together to make a cloth. Then a low densitypolyethylene is coated over the “cloth” to make it water tight. It willbe understood that there are a myriad of woven coated and film polymerswhich can be used as the geomembrane of the present invention.Geotextile sheet 15 is substantially any geotextile, but is, in thisembodiment, a non-woven polypropylene (felt) material beingapproximately 8 oz per square yard.

Ground cover 10 is positioned on an area to be protected withgeomembrane sheet 12 adjacent soil 20 and geotextile sheet 15 in anoverlying relationship and presenting a secure footing upon whichtraffic can move and work can be performed. In this specific embodiment,geomembrane sheet 12 should be of sufficient thickness to preventpunctures and ripping by contact with the underlying soil 20. Adhesivelayer 18 bonds the entire overlying area of surfaces 14 and surface 16together, securely holding geomembrane sheet 12 and geotextile sheet 15immobile relative one another under standard foot traffic. Adhesivelater 18 employs an adhesive which does not fully cure, remaining“tacky” when ground cover 10 is deployed. The adhesive strength and therelease point of the adhesive is vital to the invention. The adhesivestrength is sufficient to securely bond geomembrane sheet 12 andgeotextile sheet 15 together under normal foot traffic and lightworkloads, while having a release point allowing separation ofgeomembrane sheet 12 and geotextile sheet 15 under heavier shear loadsresulting from heavy machinery or vehicles. To achieve this balance, ithas been determined that a hot melt pressure sensitive adhesive such asthat supplied by HB Fuller HL-2811 and HL-2081 can be used. Theseproducts function with a base ingredient of a synthetic rubber whichproduces the flexibility. This is augmented with hydrocarbon resinswhich produce the specific adhesion and tack of each formula.Hydrocarbon oil is also included to provide the permanent qualities ofthe pressure sensitivity. To achieve the desired adhesion and separationpoint, the adhesive is applied in an amount of 0.01 to 0.1 ounce persquare foot of surface. In the preferred embodiment, with the preferredadhesive, approximately 0.017 ounce of adhesive is applied per squarefoot. The adhesive must be melted and applied prior to adheringgeomembrane sheet 12 to geotextile sheet 15.

In this manner, workers and other individuals can work and move aboutupon ground cover 10 without being subject to slipping or trippinghazards. Geomembrane sheet 12 is protected from damage by foot trafficand dropped tools and the like as well as protected from damage by heavyequipment such as vehicles and the like by geotextile layer 15.Additionally, pinching or tearing of geomembrane layer 12 resulting fromshear forces exerted on geotextile sheet 15 by heavy machinery andvehicles is prevented by an intentional separation 22 (FIG. 2) ofgeotextile sheet 15 from geomembrane sheet 12 in the area of shear forceapplication. In other words, if for example, a moving tire is turned onground cover 10, shear forces generated by the turning tire wouldnormally cause a tear or pinch in geomembrane sheet 12. By permittinggeotextile sheet 15 to separate from geomembrane 12 in this area, theshear forces will be dissipated in the geotextile sheet 15, leaving thegeomembrane sheet 12 undamaged. Once the shear force has been removed,the portion of geotextile sheet 15 separated from geomembrane sheet 12will return to a normal position, and will re-adhere to geomembranesheet 12. It will be understood that while ground cover 10 has beendescribed with geomembrane sheet 12 adjacent soil 20, ground cover 10can be inverted if desired, with geotextile sheet 15 adjacent soil 20.

Ground cover 10 can also be easily repaired by cutting out a damaged orcontaminated portion of geotextile sheet 15 and peeling it from thegeomembrane sheet 12. If there is insufficient adhesive from adhesivelayer 18 remaining, additional adhesive can be applied as necessary anda replacement portion of geotextile adhered into position on geomembranesheet 12. Additional adhesive can be applied by providing an adhesiverepair layer 25. Referring to FIG. 3, adhesive repair layer 25 isprovided by depositing the adhesive, such as by spraying, betweenspecially coated papers 28, 29, such as “wax paper”. When a contaminatedor damaged section of geotextile sheet 15 must be replaced, the sectionis cut out, one of the coated papers 28 is removed, the adhesive repairlayer 25 on the remaining paper 29 is adhered to a replacement sectionof geotextile and the remaining paper 29 peeled away leaving adhesiverepair layer 25 affixed to the replacement section. The replacementgeotextile section can then be adhered to exposed geomembrane sheet 12.In this manner, repairs to ground cover 10 can be undergone without theneed for a hot glue gun in the field.

It will also be understood that large areas may need to be covered byground cover 10. If the area is larger than can be efficiently handleswith one section of ground cover 10, multiple section of ground cover 10may need to be positioned adjacent one another and sealed together. Toaccomplish this, a strip of geotextile sheet 15 can be removed from theadjacent edges of the sections and the geomembrane sheets 12 heat bondedtogether to form a leak proof seal. Any exposed geomembrane can becovered by geotextile 15 using the above described repair technique.

Turning now to FIG. 4, it can be seen that multiple layers of materialcan be employed in a ground cover generally designated 40. Ground cover40 includes includes a geomembrane sheet 42 having opposing surfaces 43and 44, a geotextile sheet 45 having a surface 46 overlying surface 43,an adhesive layer 48 carried between surface 43 and surface 46, anothergeotextile sheet 50 having a surface 52 overlying surface 44, and anadhesive layer 53 carried between surface 44 and surface 52. Asdescribed previously, the adhesion strength between geomembrane sheet 42and geotextile sheets 45 and 50 is essential to the invention. Bysandwiching geomembrane sheet 42 between geotextile sheets 45 and 50,geomembrane sheet 42 is offered better protection.

Various changes and modifications to the embodiments herein chosen forpurposes of illustration will readily occur to those skilled in the art.To the extent that such modifications and variations do not depart fromthe spirit of the invention, they are intended to be included within thescope thereof, which is assessed only by a fair interpretation of thefollowing claims.

Having fully described the invention in such clear and concise terms asto enable those skilled in the art to understand and practice the same,the invention claimed is:
 1. A ground cover for use as a containmentbarrier comprising: a geomembrane sheet having a first surface and asecond surface; a geotextile sheet having a surface overlying the firstsurface of the geomembrane sheet; and an adhesive layer positionedbetween the first surface of the geomembrane sheet and the surface ofthe geotextile sheet, wherein the adhesive layer does not fully cure andremains tacky, the adhesive layer having an adhesive strength sufficientto maintain a bond between the geomembrane sheet and the geotextilesheet under normal foot traffic and a release point allowing separationof the geomembrane sheet and the geotextile sheet under shear forcesgenerated by heavier traffic.
 2. A ground cover as claimed in claim 1wherein the adhesive layer is present in an amount of 0.01 to 0.1 ounceper square foot of surface.
 3. A ground cover as claimed in claim 1wherein the adhesive layer is present in the amount of approximately0.017 ounce per square foot.
 4. A ground cover as claimed in claim 1wherein the adhesive layer is a pressure sensitive adhesive.
 5. A groundcover as claimed in claim 1 further including a second geotextile sheethaving a surface overlying the second surface of the geomembrane sheet.6. A ground cover as claimed in claim 5 further including a secondadhesive layer positioned between the second surface of the geomembranesheet and the surface of the second geotextile sheet.
 7. A ground coveras claimed in claim 6 wherein the adhesive layer does not fully cure andremains tacky, the adhesive layer having an adhesive strength sufficientto maintain a bond between the geomembrane sheet and the geotextilesheet under normal foot traffic and a release point allowing separationof the geomembrane sheet and the geotextile sheet under shear forcesgenerated by heavier traffic.
 8. A ground cover as claimed in claim 7wherein the adhesive layer is present in an amount of 0.01 to 0.1 ounceper square foot of surface.
 9. A ground cover as claimed in claim 7wherein the adhesive layer is present in the amount of approximately0.017 ounce per square foot.
 10. A ground cover for use as a containmentbarrier comprising: a geomembrane sheet having a first surface and asecond surface; a first geotextile sheet having a surface overlying thefirst surface of the geomembrane sheet; a second geotextile sheet havinga surface overlying the second surface of the geomembrane sheet; anfirst adhesive layer positioned between the first surface of thegeomembrane sheet and the surface of the first geotextile sheet, whereinthe adhesive layer does not fully cure and remains tacky, the adhesivelayer having an adhesive strength sufficient to maintain a bond betweenthe geomembrane sheet and the first geotextile sheet under normal foottraffic and a release point allowing separation of the geomembrane sheetand the first geotextile sheet under shear forces generated by heaviertraffic; and a second adhesive layer positioned between the secondsurface of the geomembrane sheet and the surface of the secondgeotextile sheet.
 11. A ground cover as claimed in claim 10 wherein thefirst adhesive layer is present in an amount of 0.01 to 0.1 ounce persquare foot of surface.
 12. A ground cover as claimed in claim 10wherein the first adhesive layer is present in the amount ofapproximately 0.017 ounce per square foot.
 13. A ground cover as claimedin claim 10 wherein the second adhesive layer does not fully cure andremains tacky, the adhesive layer having an adhesive strength sufficientto maintain a bond between the geomembrane sheet and the secondgeotextile sheet under normal foot traffic and a release point allowingseparation of the geomembrane sheet and the second geotextile sheetunder shear forces generated by heavier traffic.
 14. A ground cover asclaimed in claim 13 wherein the second adhesive layer is present in anamount of 0.01 to 0.1 ounce per square foot of surface.
 15. A groundcover as claimed in claim 13 wherein the adhesive layer is present inthe amount of approximately 0.017 ounce per square foot.